Canavanine and canaline are nonprotein amino acids and the naturally occurring guanidinoxy and aminooxy structural analogues of arginine and ornithine respectively. Arginine, ornithine, canavanine and canaline are probably synthesized by the enzyme complement responsible for urea production via the ornithine-urea cycle. Fundamental studies of the interrelationships of these amino acids to the enzymes mediating their biosynthesis are planned. The antimetabolic properties of canavanine and canaline will be studied both in canavanine-containing species and in mammalian tissues and cultured mammalian cell lines.